Hydrobromic acid is widely used as an intermediate in the chemical industry. It is utilized in the production of inorganic bromides by reaction with metal hydroxides, oxides, or carbonates; in the production of organic bromides by reaction with alkyl alcohols or alkenes; and as a catalyst for oxidations, alkylations, and condensations in organic chemistry.
Sodium bisulfate is an industrial and household acidulant with many different uses, including toilet bowl cleaners, cleaning compounds, swimming pool pH adjustment, pulp and paper processing, metal finishing, and food and beverage additives.
In the past, halogenated acids such as hydrobromic acid have been prepared in gaseous form by several laboratory methods such as direct combination of hydrogen and bromide, using platinized silica gel as a catalyst; bromination of organic compounds such as benzene, naphthalene, or tetrahydro-napthalene; and reacting bromine with red phosphorus and water. None of these processes are practical for the industrial production of hydrobromic acid. The first process is generally expensive and presents a considerable explosion hazard. The second process is inefficient and costly in that it typically utilizes only about half of the expensive bromine employed. The last is apt to be violent, difficult to control, and may present a serious explosion hazard.
Currently, there are two main approaches for the industrial production of hydrobromic acid. The first approach is a two conversion process whereby low purity, natural deposits of sodium bromide are converted first into elemental bromine and second into hydrobromic acid. The first conversion is done by oxidation with chlorine, where the sodium bromide is converted into sodium chloride and bromine by the reaction:2NaBr+Cl2→2NaCl+Br2According to Stanford Research Institute's Chemical Economics Handbook, commercial bromine suppliers such as Great Lakes Chemicals (located in El Dorado and Marysville, Ak.), Albemarle (located in Magnolia, Ak.), and Dead Sea Bromine Co. (located in Sdom, Israel), currently practice this step. A second conversion involves either (a) burning bromine and hydrogen to form hydrobromic acid, such as discussed in Ullman's Encyclopedia of Industrial Chemistry, 5th edition, 1985, Volume A4, pg. 396, according to the reaction:Br2+H2→2 HBror (b) by an electrolytic process whereby a solution of bromine is converted into hydrobromic acid and oxygen (as disclosed in U.S. Pat. Nos. 4,069,120 to United Technologies Corporation, issued Jan. 17, 1978 and 4,203,813 to United Technologies Corporation, issued May 20, 1980), according to the reaction:2Br2+2H2O→4HBr+O2This two conversion process to produce hydrobromic acid has a number of drawbacks. First, operating and capital costs are high since a separate manufacturing plant is employed for each conversion. In addition, if bromine burning is implemented, free bromine is often present in the hydrobromic acid product, resulting in a product with the characteristic yellow and/or orange color associated with free bromine. This is generally unacceptable for applications requiring a colorless hydrobromic acid product.
The second approach for chemical manufacture of hydrobromic acid is a one conversion process whereby high purity sodium bromide is reacted with sulfuric acid (U.S. Pat. Nos. 1,379,731 to Lowenstein Radio Corporation, issued May 31, 1921 and U.S. Pat. No. 2,705,670 to American Cyanamid, issued Apr. 5, 1955) according to the reaction:NaBr+H2SO4→HBr+NaHSO4This approach is well suited for industrial companies which wish to convert high purity sodium bromide to hydrobromic acid and sodium bisulfate products. However, this approach has a number of drawbacks as well. First, if the hydrobromic acid is of low purity, then product applications are limited and/or capital and operating costs are high to purify the material. This can occur if (a) significant levels of bromine are generated from hydrobromic acid via the following reaction,2 HBr+H2SO4→Br2+SO2+2H2Oor, (b) the hydrobromic acid is not sufficiently free of water. Second, if the sodium bisulfate salt is of low purity, then product applications are limited and/or capital and operating costs are high to purify this material as well. This can occur if (a) iron bromide is present in the sodium bisulfate at levels sufficient to impart an orange color to the product, (b) significant quantities of sodium bromide or hydrogen bromide are left in the sodium bisulfate, (c) a significant portion of sodium bisulfate reacts with sodium bromide to produce sodium sulfate, according to the reaction:NaHSO4+NaBr→HBr+Na2SO4or, (d) the sodium bisulfate undergoes decomposition to sodium pyrosulfate via the following reaction,2 NaHSO4→Na2S2O7+H2O
Therefore, there is a continuing need for an improved process approach for making anhydrous hydrobromic acid and sodium bisulfate. Specific areas for improvement vs. current commercial processes include improving product purity, reducing operating cost, and reducing capital cost.